Location: Fruit and Nut ResearchTitle: Optimization of a host diet for in vivo production of entomopathogenic nematodes Author
Submitted to: Journal of Nematology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/28/2011
Publication Date: 8/1/2012
Citation: Shapiro Ilan, D.I., Rojas, M.G., Morales Ramos, J.A., Tedders, L.T. 2012. Optimization of a host diet for in vivo production of entomopathogenic nematodes. Journal of Nematology. 44:264-273. Interpretive Summary: Entomopathogenic (insect-killing) nematodes are small round worms that are used as environmentally safe bio-insecticides. In order to improve the use of these nematodes in sustainable pest control approaches, it is important to develop better methods of producing quality nematode products. Entomopathogenic nematodes can be grown in artificial media (in vitro) or in insect hosts (in vivo). The goal of this study was to determine the effects of insect diet on in vivo production of entomopathogenic nematodes. We discovered that an insect diet that was improved for efficient production of mealworms can also translate into superior fitness in nematodes that are cultured on the mealworms. Thus, the overall in vivo production system for entomopathogenic nematodes can be enhanced by using the improved insect diet. Improved production of entomopathogenic nematodes will lead to superior biological pest control efforts.
Technical Abstract: In previous studies, we developed an improved diet for Tenebrio molitor, a host that is used for in vivo nematode production, and we demonstrated that single insect diet components (e.g., lipids and proteins) can have a positive or negative impact on entomopathogenic nematode fitness and quality. In this study, we tested components of our improved T. molitor diet (lipids, cholesterol, and a salt [MnSO4]), alone and in combination for effects on host susceptibility and reproductive capacity of Heterorhabditis indica and Steinernema carpocapsae. Our results indicated that moderate levels of lipids (10%) increased host susceptibility to S. carpocapsae but did not affect H. indica, whereas cholesterol and MnSO4 increased host susceptibility to H. indica but not S. carpocapsae. The combined T. molitor diet (improved for increased insect growth) increased host susceptibility to S. carpocapsae and had a neutral effect on H. indica; interactions among single diet ingredients were observed. No effects of insect host diet were detected on the reproductive capacity of either nematode species in T. molitor. The progeny nematodes produced from differing T. molitor diet treatments did not differ in virulence except H. indica derived from a diet that lacked cholesterol or MnS04 (but contained lipids) did not cause significant D. abbreviatus suppression relative to the water control. We conclude that the improved insect host diet is compatible with production of H. indica and S. carpocapsae, and increases host susceptibility in S. carpocapsae. Furthermore, in a general sense, our results indicate host diets can be optimized for improved in vivo entomopathogenic nematode production efficiency. This is the first report of an insect diet that was optimized for both host and entomopathogenic nematode production. Additionally, our study indicates that host diet may impact broader aspects of entomopathogenic nematode ecology and pest control efficacy.